Crystalline titanium dioxide nanoparticles generally having an average particle size of 50 nm or less, which is a representative material for a photo-catalyst, have been spotlighted as a new energy environmental material having characteristics such as decomposition of a harmful ingredient, an antibiotic property, deodorization, and the like, using ultraviolet (UV) light as an energy source. Recently, raw materials and usage of the crystalline titanium dioxide nanoparticles as described above have been rapidly developed.
A general preparation method of titanium dioxide may be divided as follows.
A sulfuric acid method is a method of sintering titanium dioxide obtained by pyrolyzing an aqueous TiOSO4 solution at 800 to 1000° C. to grow particles to thereby obtain TiO2 particles having a desired size. In the case of the sulfuric acid method, waste sulfuric acid may be generated during a process, thereby causing an environmental problem, and micro-fine titanium dioxide particles may be prepared by physical grinding, but titanium dioxide particles of which purity is deteriorated due to impurities may be produced. Therefore, the sulfuric acid method may not be used for a raw material for storing energy or a precise material for a multilayer ceramic capacitor (MLCC), or the like.
A hydrochloric acid method is a method of reacting heated TiCl4 vapor with heated oxygen to form TiO2 particles in a high temperature vapor phase. In the case of the hydrochloric acid method, since precipitated particles formed by a high temperature reaction are used, only particles having a rutile crystalline phase are prepared, expensive equipment for collecting hydrochloric acid gas and a chlorine control technology are required, and a risk due to hydrochloric acid gas in the process may be high.
Otherwise, there are methods of using alkoxides or high temperature vapor phases such as a sol-gel method, a spray flame method, and a chemical vapor deposition method, but these methods are not significantly useful due to a high process cost and low productivity.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.